Convert more tests into text-based-repaint tests

LayoutTests/compositing/repaint/invalidations-on-composited-layers-expected.txt

 {
   "bounds": [800, 600],
   "children": [
     {
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
-      "repaintRects": [
-        [8, 413, 784, 28],
-        [8, 13, 784, 15],
-        [0, 421, 800, 28]
-      ],

[Xianzhu, 2014/07/21 18:33:37]

This was extra repaints caused by the output of layer tree.

       "children": [
         {
-          "position": [8, 41],
+          "position": [8, 8],

[chrishtr, 2014/07/21 19:05:34]

What about this change? Why does it happen?

[Xianzhu, 2014/07/21 19:15:24]

This is because there is no more layer-tree-text (which was actually a noise)
above it.

           "bounds": [400, 400],
           "contentsOpaque": true,
           "drawsContent": true,
           "backgroundColor": "#008000",
           "repaintRects": [
             [0, 0, 400, 400],
             [0, 0, 400, 400]
           ],
           "children": [
             {
               "position": [50, 50],
               "bounds": [75, 75],
               "contentsOpaque": true,
               "drawsContent": true,
               "backgroundColor": "#0000FF",
               "repaintRects": [
                 [0, 0, 75, 75],
                 [0, 0, 75, 75]
               ]
             }
           ]
         }
       ]
     }
   ]
 }